5-nitrotetrahydro-1, 3-oxazines and method for preparing them



Patented Aug. 24, 1948 -NITROTETRAHYDRO 1,3 OXAZINES AND METHOD FOR PREPARING THEM Murray Senkus, Terre Haute, Ind, assignor to Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing. Application February 25, 1946, Serial No. 650,134

1 12 Claims.

My invention relates to a new series of chemical compounds. More particularly it relates to S-nitrotetrahydro-1,3-oxazines and to a process for the production thereof. The compounds of my invention may be represented by the following structural formula:

6 H1O H: No, R in which R1 is a member of the group consisting of alkyl, aralkyl, cycloalkyl, Z-hydroxyalkyl, 3,5- dioxacyclohexyl, and 3,5-diazacyclohexy1 and R is a member of the group consisting of hydrogen, alkyl, aryl, aralkyl, and hydroxymethyl.

Typical examples of the 5-nitrotetrahydro-1,3- oxazines of my invention represented by the above formula include: 5-nitro-3-(1,3,5-trimethyl-3,5- diazacyclohexyl) -5-methyltetrahydro 1,3 oxazine, 5-nitro-5-methyl 3 cyclohexyltetrahydro- 1,3-oxazine, 5-nitro-3-(1-methyl-3,5-dioxacyolohexyl)-5-methyltetrahydro-1,3-oxazine, 5-nitro- 3,5-dimethyltetrahydro-1,3-oxazine, 5 nitro-5- methyl-3-isopropyltetrahydro-1,3-oxazine, 5-mtro-5-isopropyl-3-benzyltetrahydro-1,3 oxazine, 5-nitro-3-methyltetrahydr0-1,3-oxazine, 5-nitro- 3-methy1-5- (hydroxymethyl) tetrahydro-1,3-oxazine, 5-nitro-5-phenyl-3-isopropyltetrahydro-1,3- oxazine, 5-nitro-5-benzyl-3-butyltetrahydro-1,3- oxazine, and 5-nitro-5-propyl-3-(l-ethyl-2-hydroxyethyl) -tertahydro-1,3-oxazine.

According to my invention, the fi-nitrotetrahydro-1,3-oxazines of the types illustrated above may be readily prepared by reacting formaldehyde, an amine and a nitroparaffin. The order and conditions of the reaction may be Varied considerably without materially affecting the course of the reaction. For example, the desired amine may first be reacted with aqueous formaldehyde to produce the N-(hydroxymethyD-amine, the latter then being reacted with the nitroparafiin to give the 5-nitrotetrahydro-1,3-oxazine If preferred, however, the three reactants may be mixed at the same time and the reaction permittedto take place. These and other modifications are illustrated in the specific examples cited below.

2 The exact mechanism whereby my new 5-nitrotetrahydro1,3-oxazines are produced is not definitely known. It appears, however, that they may be produced by either of the following procedures, depending upon the starting materials employed.

III R NH H Hz-Rz H0110 ---i NO: Formaldehyde 5-nitrotetrahydro-1,3-oxazine As will be evident from the following equations the same result can be attained even though the reaction follows a somewhat difierent course.

I RNH1 HCHO Amine Formaldehyde I Nitroparaflfln Formaldehyde N0:

Using a nitroalkanediol in place of a nitroparaffin the reaction appears to take place as follows:

Amine Formaldehyde CHzOH CHzOH R CH20H Rz-CH ECHO II (b) N02 Nitroalkanediol III(b) CHzOH R NH CHzOH N02 l lOz methyl) amine .inthe .first step, :the ,formalde-q hyde is preferably first added. to a cooled solution-of therequired amine .inthe .ratioof threemoles of the former to one of the latter This reaction is generally quite exothermic in nature and it is usually desirable to cool the reaction vessel with ice or by otherqsuitable means, particularly if volatile .lowqmolecular weight amines are employed. When the reaction has subsided, a suitable nitroparaflin having the nitro group attached to a -primary carbon-:"atom is added in a molar concentration equivalent to that of the amine. After all of the nitroparaffin has been introduced, -the reaction mixture isgenerally heated to about 70, C., in order-v to drive the reaction to completion. The reaction, however, may becarried to completion without heating merely by, permitting the reaction ,mixture to stand at roomrtemperature fora numbenof hours, e..,g., 10-15. hours, Uponcompletion of the reaction, the 5-nitrotetrahydro-1,3-oxazines are recovered-by crystallization from a suitable solvent such as aliphatic or aromatic hydrocarbons, alcohols, .or ethers, the choice of particular solvent depending to some extent upon the molecular, Weightofthe 5-nitrotetrahydro-.-1,3-. oxazines tobe recovered and purified.

A modified and frequently preferredjprocedure for preparing the 5-nitrotetrahydro-1,3-oxazines of my invention, involves mixing. a nitroalkanediol with a suitable primary amine, the two materials being preferably brought together in a ratio of 1 mole; of amine to one mole of nitroalkanediol. Under these conditions,- the nitroalkanediol dissociates into-the .parent' nitroparaffin and, formaldehyde,..thus resulting in the formation of :the reaction mixture containing an amine, a nitroparafiin," and formaldehyde. In the case ofraromatic aminesa small quantity of catalyst, such as 50% aqueous sodium hydroxide,

be employ d ;in my -processzand -the structure of should be employed. Thereafter, formaldehyde in the formof an aqueous solution, or trioxymethlene, is addedtothe mixturein 'anamount corresponding approximately to the .;molec11lar quantity of nitroalkanediol present. Upon completion of thereaction the product is recovered as previously indicated.

Since the procedures described above result in they each fundamentally involve reaction mixtures containing formaldehyde, a primary amine, and a nitroparafiln having the nitro group attached to a primary carbon atom, it may be seen that the reactions occurring therein are in all essential respects equivalent. It is therefore to be specifically understood that the terminology employed in certain of the appended process claims is to be construed to cover both of the foregoing modifications.

While I have'indicated 'above that it is desirable to use at least three moles-of formaldehyde for each mole of nitroparaffin in the preparation of-the compounds of my invention, it is possible ,toseffectvthe desired reaction by employing lower propontions.ofi'formaldehyde, such as for example, two moles for each mole of nitroparafiin. The yieldsof 5- hitrotetra'hydro-1,3-oxazines obtained, however;*undensuch-conditions are lower. The ratioof amine to'nitroparaffin and formaldehyde may; also be-varied somewhat. It should be noted, .ho1wever ,:that increasing the ratio of amine substantiallyabove the proportions indicated above, namely'one-mole of amine to one mole of nitroparafiin to three moles of-formaldehyde, results in an appreciable increase in the formation of 5-nitrohexahydropyrimidines; which are pro duced-"tosome extent even with the-ratios of reactants specifiedabove and which are 'apparent'lyprimarilyi produced-when the ratios of the reactants reach the proportions-of one mole of nitroparaffln to two moles of amines to three moles of formaldehyde.

Reaction temperatures maybe employed ranging from about 25-30".C. to arefiux temperature of the reaction mixture, theselection of temperature being dependent largely on the particular process utilized and the molecular weight of the primaryzanune.em-ployedn It--maybe mentioned, however; ithat-reaction between-substantially any amine and nitroparaflinmay be effected at roomtemperature; in the presence of, formaldehyde if the reactantsare.permittedtoremain in contact-- v witlroneanothertfor'a suficient period of time.-.

Thereaction generally; can be effected in theabsence; of, a solvent: 1 However, I have found it 1 preferable: inmost instances to, employ suitable, solvents such asybenzene or a lowertaliphatic alcoe.

h'OLgi.

Anyqrprimaryamine; aliphatic-or aromatic, can

any .-particular amine. utilized ,nnay .vary Widely.

Forl instance, in addition toathe utilization of any of theycommonaliphatic.or aromatic aminessuch as methyla'mine;,-ethylarnine, butylamine, cyclohex-ylamine;benzylamine; aniline, naphthylamine, Y

z-amino -l -butanol, .-and.the like,- I may also employyvith equal success certain'aromatic diamines,

such as N-(2-aminoisobutyll ,-N- methy1-o-chl0-" I'-OaI-1i1ine,'-N-.= (2-ami-noisobutyl) -N-methyla'niline,

N (-2-;am-inoisobutyl) Ni-methyl-m-toluidine, N- (2-aminoisobutyl) elfl-ethyl-p-aminobenzoic acid, 1 and1=N'-:"( 2 aminoisobutyl) N e methylsulfanilicacid; and aliphati czdiamines'. such asN- (2-aminoisobutyD-dimet-hylamine; 3. N (2 aminoisobutyl) isopropylmethylamine :N ;(2+aminoisobutyl) bis' (1 -rmethylhexyl) amine, .:;N+2 ('aminoisobutyl) diocta'decylaminegfiN fZ-aminoisobutyl) benzyl'e methylamlne; N-i( z aminoisobutyl) '-N-(1-phenyl-= ethyl) methylamine,-= N (2'- aminoisobutyl) cyclohexylmethylamine,- N-(2=aminoisobutyl)' N (1- methylcyclohex-yl) methylarnine, 1 5-amino-3-be'nzyl-2,2.5L'trimethyl 3-aza l-hexan 01, N- 2-amino- I bisttetrahydrofurfuryl)amine, =N -'(2=* the formationof identical-products, and since 'aminoisobutyl)difurfurylamine, N 2 aminoiso isobutyl) butyl) piperidine, N-(2-an1inoisobutyl) 2,5 dimethylpyrrolidine, N- (Z-aminoisobutyl) morpholine, and the like.-

I may also satisfactorily employ amino compounds such as 5-amino-5-methyl-1,3-dioxane and 5-aminohexahydropyrimidines of the type disclosed inmy U. S. Patent No. 2,387,043, granted October 16,1945.

The group of amines which I have designated asaromatic diamines may be conveniently prepared by catalytic reduction of the corresponding nitro amines under pressure, as described in copending application, U. S. Serial No. 571,955, filed January 8, 1945, by Harold G. Johnson. The nitro aa'nin'es employed as starting materials for the synthesis of the aforesaid aromatic diamines may be prepared in accordance with the procedure described in copending application, Serial No. 571, 954, filed January 8, 1945, by Harold G. Johnson. According to this procedure, a secondary aromatic amine is reacted with a suitable monoor dihydric primary nitro alcoholin the presence of a basic catalyst, such as for example, sodium hydroxide, tributylamine, triethylamine, or benzylammonium hydroxide at a temperature of approximately 50 C.

The amines designated above as aliphatic diamines can readily be synthesized by cathalytically reducing the corresponding nitro amines under pressure in accordance with the procedure described and claimed in my copending applicaton, U. S. Serial No. 455,932, now Patent No. 2,393,825, filed August 24, 1942. The nitro amines utilized as starting materials may be synthesized in accordance with the procedure described in my copending applications, U. S. Serial Nos. 579,894, now Patent No. 2,419,506, 579,895, 579,896, 579,897, all filed February 26, 1945. By this procedure a secondary aliphatic amine is reacted with formaldehyde to form the corresponding N-hydroxymethyl monoor dialkylamine, which is in turn reacted with an equimolecular quantity of a secondary nitroparafiin to produce the desired nitro amine. The preparation of such nitro amines is preferably carried out at temperatures of from between about 25-30 C. Temperatures above this range may be utilized but in doing so care should be exercised to avoid temperatures which cause the formaldehyde to be volatilized from the reaction mixture.

As examples of suitable nitroparafilns which may be employed in my process, there may be mentioned nitromethane, nitroethane, 1- nitropropane, l-nitrobutane, l-nitroisobutane, l-nitro-2-phenylethane, phenylnitromethane, and the like.

The process of my invention may be more specifically illustrated by the representative examples which follow:

Example I To 117 g. of 5-amino-5-methyl-1,3-dioxane (1 mole) was added 225 m1.- of 36% aqueous formaldehyde (3 moles). The temperature rose to 50 C. several minutes after the aldehyde had been added and then began to fall. To the mixture '75 g. of nitroethane (1 mole) was then added. The temperature of the mixture rose from 40 C. to 60 C. in thirty minutes. At this point it turned cloudy. The mixture was stirred for six hours and then was allowed to stand an additional six hours. The crystalline product which separated from the mixture was filtered, washed with 500 ml. of methanol and cooled to 0 C. The solid was recrystallized from 500 ml. of methanol, and

6 dried in air for twenty-four hours; yield, 88 g. Analysis of the final product showed it to be. a mixture of 5 nitro -3- (1-methyl-3,5-dioxacyclohexyl)-5-methyltetrahydro-1,3-oxazines and 5- nitro l,3-bis(l methyl-3,5-dioxacyclohexyl) -5- methylhexahydro-pyrimidine. Further crystallization from methanol gave the pure 5-nitrotetrahydro- 1,3-oxazine.

Example II To 270 g. of 2-nitro-2-methyl-1,3-propanediol (2 moles) was added 200 g. of 30% aqueous methylamine (2 moles). After the nitro glycol had dissolved, 160 ml. of 36% aqueous formaldehyde were added to the mixture and the solution was allowed to stand in the room for a week. The solution was extracted with one liter of ether and the ether extract was washed with two500 ml. portions of water. The washed ether extract was heated on the steam bath in order to remove the ether. The residue weighed 130 g. and consisted primarily of 5-nitro-3,5-dimethyltetrahydro-1,3-oxazine.

Example III To 59 g. of isopropylamine (1 mole) was added 75 ml. of 36% aqueous formaldehyde (1 mole). The mixture was cooled by external means during the addition of aldehyde. The non-aqueous layer was separated and was found to weigh 70 g. (0.79 mole of N-(hydroxymethyl)isopropylamine, assuming purity). To this layer was added g. of 2-nitro-2-methyl-1,3-propanediol (0.79 mole) and 500 ml. of benzene. The mixture was distilled slowly and the water from the reaction was removed. After water had ceased distilling, 500 ml. of petroleum ether was added to the residue and the solution was washed with three 500 ml. portions of water. Rectification of the washed solution gave 81 g. of 5-nitro- 3-isopropyl-5-methyltetrahydro-1,3-oxazine, B. P. 83-85 C. at 0.3 ml.

The 5-nitrotetrahydro-1,3-oxazines of the type illustrated and discussed above are useful in the preparation of numerous valuable organic compounds. Additional uses of these materials will be apparent to those skilled in the art.

My invention now having been described, what I claim is:

1. A process for the preparation of 5-nitrotetrahydro-l,3-oxazines, which comprises bringing a primary amine into reaction with a nitroparaflin having a nitro group attached to a primary carbon atom, in the presence of formaldehyde, the latter being employed in a ratio of at least two moles to one mole of nitroparaffin and one mole of primary amine, and separating and recovering the E-nitrotetrahydro-1,3-oxazines thus formed.

2. A process for the preparation of 5-nitrotetrahydro-LB-oxazines, which comprises bringing a primary amine into reaction with a nitroparafiin having 2. nitro group attached to a primary carbon atom, in the presence of formaldehyde, the latter being employed in a ratio of at least three moles to one mole of nitroparafl'ln and one mole of primary amine, and separating and recovering the E-nitrotetrahydro-1,3-oxazines thus formed.

3. A process for the preparation of 5-nitrotetrahydro-1,3-oxazines, which comprises adding formaldehyde to a primary amine to produce the corresponding N-hydroxymethylamine, and thereafter adding to the resulting mixture a nitroparaifin having the nitro group attached to a :pnimary carbon atnm, the :form-aldehyde being added in :-a ratio of {at )least :three moles to ione male of :riitroparafiin :and .one mole ;of primary amine, and separating and recovering the nitrotetliahydrmlfi-oxazines thus formed.

A. A process for the preparation of Ea-nitrotet-raih-yclro-1,3-oxazines, which comprises mixing a primary amine with a 2=nitro-l,3-propanediol in a molecular ratio of approximately one mole of said amine to one .of 2-n'itro-1,3-propanedi0l in the presence of formaldehyde, the remainder of the formaldehyderequiredforthe preparation of the desired 5-,nitrotetrahydro-1,3-oxazines being furnished by the decomposition of said 2- nitro=1j3-propanediol into formaldehyde and a nitroparafiin having the 'nitro group attached to a primary carbon atom, and separating and recovering the *5enitrotetrahydro-1;3-0xazines thus formed.

'5. A 'process for the preparation of 5-nitrotetrahydno-LB-oxazines, which comprises mixing a primary amine with .a Z-nitro-l,'3-propanediol in a molecular ratio of approximately one mole of said amine to one of said 2-nitr0-'1,3-propanedial in the presence of at least :one mole of formaldehyde, the remainder of the formaldehyde required for 'the'preparat-ion of thedesired 5-ni'trotetrahydro-'1,3-oxazines "being furnished by the decomposition of said '2-nitro-1,3-propanedi0l into formaldehyde and nitroparafiin having the 8 nitro igroup attached to :a primary :camhomatom, and separating and recovering the Emitrotetrahydro-1,3-oxazines thus formed.

6. The process of claim 3 in which the nitroparaflin is nitroethane and the primary amine is .5eamino-5-methyl-L3-dioxane.

7,. The process of claim 4 inwhich the '2-.nitro- 1,3-propaneclio1 is Z-nitro-2-methyl-=1,3 propanediol and the primary vamine .is ,methylamine.

8. The process of claim A in which the 2-.nitro- 1,3-ppanediolis.Z-nitro2-methyI L3 pr panediol and the primary amine is .isopropylamine.

9. .Asvnew vcompositions of matter, 5-nitro'tetrahydro-LS-oxazines.

'10. 5-nitro-'3;5-d'imethy1tetrahydro 1,3 oxazme.

1"1. 5--nitr0 3- isopropyl-5-methyltetrahydro- 1,3-"oXaZtine.

12. 5-nitro-3-'(1amethyl-3,5 dioxacyclohexy1) 5-:methyltetra'hydro-1,'3-oxazine.

"MURRAY' SENKUS.

' REFERENCES CITED UNITED STATES PATENTS Name I Date .Senkus M... 'Dec. '25, 1945v Number Certificate of Correction Patent No. 2,447,322. August 24,- 1948.

MURRAY SENKUS It is herebyfcertified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 1, line 34, for tertahydro read tetrahydro; column 3, line 69, for methlene read methylene; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of November, A. D. 1948.

THOMAS F. MURPHY,

Asaistant O'ommz'ssioner of Patents. 

